Worst service tech and phone are useless

Had xfinity prepaid modem kept loosing connection , get a new self bought nice modem told its only xfinity (not prepaid) compatible, so I start a xfinity account , new modem better service , should be better right? WRONG. Hasnt worked not once (and yes was installed correct as it shows im online but loose all service other than power over and over 5 times in 20 mins On phone with tech support 2 diff techs “outside” cause of covid cant come in they said when he pulled up all red flags 20 mins after him leaving its doesn't work at all . I only have 1 tv and ipad neither can play a video more than 2 mins without loosing internet. Landlord said there was a post problem 2 years ago, Xfinity telling me its inside wiring but CANT come in to check now my son is failing school cause we cant get his work!! Ready to see if fios is better considering the other 2 floors in my house dont have the same issue with fios